Embolic filtering devices for bifurcated vessels

ABSTRACT

An embolic filtering device for use in a bifurcated vessel includes delivery device having a first guide wire and a second guide wire. The second guide wire diverges from the distal-end region of the first guide wire. The filter device also includes a filter support having a first deployment member and a second deployment member. These deployment members can be formed as a first loop and a second loop. A bifurcated filter element is coupled to the filter support. The distal-end region of the first guide wire extends through a first leg of the filter element and the second guide wire extends through a second leg of the filter element. During use, the first leg of the filter element is deployed within a first branch of the bifurcated vessel and the second leg of the filter element is deployed within a second branch of the bifurcated vessel.

BACKGROUND OF THE INVENTION

The present invention relates generally to filtering devices used whenan interventional procedure is being performed in a stenosed or occludedregion of a biological vessel to capture embolic material that may becreated and released into the vessel during the procedure. The presentinvention is more particularly directed to an embolic filtering devicefor use in a bifurcated vessel, such as, for example, a renal artery orcarotid artery.

Numerous procedures have been developed for treating occluded bloodvessels to allow blood to flow without obstruction. Such proceduresusually involve the percutaneous introduction of an interventionaldevice into the lumen of the artery, usually by a catheter. One widelyknown and medically accepted procedure is balloon angioplasty in whichan inflatable balloon is introduced within the stenosed region of theblood vessel to dilate the occluded vessel. The balloon dilatationcatheter is initially inserted into the patient's arterial system and isadvanced and manipulated into the area of stenosis in the artery. Theballoon is inflated to compress the plaque and press the vessel wallradially outward to increase the diameter of the blood vessel, resultingin increased blood flow. The balloon is then deflated to a small profileso that the dilatation catheter can be withdrawn from the patient'svasculature and the blood flow resumed through the dilated artery. Asshould be appreciated by those skilled in the art, while theabove-described procedure is typical, it is not the only method used inangioplasty.

Another procedure is laser angioplasty which utilizes a laser to ablatethe stenosis by super heating and vaporizing the deposited plaque.Atherectomy is yet another method of treating a stenosed biologicalvessel in which cutting blades are rotated to shave the deposited plaquefrom the arterial wall. A vacuum catheter during this procedure.

In the procedures of the kind referenced above, abrupt reclosure mayoccur or restenosis of the artery may develop over time, which mayrequire another angioplasty procedure, a surgical bypass operation, orsome other method of repairing or strengthening the area. To reduce thelikelihood of the occurrence of abrupt reclosure and to strengthen thearea, a physician can implant an intravascular prosthesis formaintaining vascular patency, commonly known as a stent, inside theartery across the lesion. The stent can be crimped tightly onto theballoon portion of the catheter and transported in its delivery diameterthrough the patient's vasculature. At the deployment site, the stent isexpanded to a larger diameter, often by inflating the balloon portion ofthe catheter.

The above non-surgical interventional procedures, when successful, avoidthe necessity of major surgical operations. However, there is one commonproblem which can become associated with all of these non-surgicalprocedures, namely, the potential release of embolic debris into thebloodstream that can occlude distal vasculature and cause significanthealth problems to the patient. For example, during deployment of astent, it is possible that the metal struts of the stent can cut intothe stenosis and shear off pieces of plaque that can travel downstreamand lodge somewhere in the patient's vascular system. Pieces of plaquematerial are sometimes generated during a balloon angioplasty procedureand become released into the bloodstream. Additionally, while completevaporization of plaque is the intended goal during laser angioplasty,sometimes particles are not fully vaporized and enter the bloodstream.Likewise, not all of the emboli created during an atherectomy proceduremay be drawn into the vacuum catheter and, as a result, enter thebloodstream as well.

When any of the above-described procedures are performed in the carotidarteries, the release of emboli into the circulatory system can beextremely dangerous and sometimes fatal to the patient. Debris carriedby the bloodstream to distal vessels of the brain can cause cerebralvessels to occlude, resulting in a stroke, and in some cases, death.Therefore, although cerebral percutaneous transluminal angioplasty hasbeen performed in the past, the number of procedures performed has beensomewhat limited due to the justifiable fear of an embolic strokeoccurring should embolic debris enter the bloodstream and block vitaldownstream blood passages.

Medical devices have been developed to attempt to deal with the problemcreated when debris or fragments enter the circulatory system followingvessel treatment utilizing any one of the above-identified procedures.One approach which has been attempted is the cutting of any debris intominute sizes which pose little chance of becoming occluded in majorvessels within the patient's vasculature. However, it is often difficultto control the size of the fragments which are formed, and the potentialrisk of vessel occlusion still exists, making such a procedure in thecarotid arteries a high-risk proposition.

Other techniques include the use of catheters with a vacuum source whichprovides temporary suction to remove embolic debris from thebloodstream. However, as mentioned above, there can be complicationsassociated with such systems if the vacuum catheter does not remove allof the embolic material from the bloodstream. Also, a powerful suctioncould cause trauma to the patient's vasculature.

Another technique which has had some success utilizes a filter or trapdownstream from the treatment site to capture embolic debris before itreaches the smaller blood vessels downstream. The placement of a filterin the patient's vasculature during treatment of the vascular lesion canreduce the presence of the embolic debris in the bloodstream. Suchembolic filters are usually delivered in a collapsed position throughthe patient's vasculature and then expanded to trap the embolic debris.Some of these embolic filters are self expanding and utilize arestraining sheath which maintains the expandable filter in a collapsedposition until it is ready to be expanded within the patient'svasculature. The physician can causing the filter to expand at thedesired location. Once the procedure is completed, the filter can becollapsed, and the filter, with the trapped embolic debris, can then beremoved from the vessel. While a filter can be effective in capturingembolic material, the filter still needs to be collapsed and removedfrom the vessel. During this step, there is a possibility that trappedembolic debris can backflow through the inlet opening of the filter andenter the bloodstream as the filtering system is being collapsed andremoved from the patient. Therefore, it is important that any capturedembolic debris remain trapped within this filter so that particles arenot released back into the biological vessel.

Some prior art expandable filters are attached to the distal end of aguide wire or guide wire-like member which allows the filtering deviceto be steered in the patient's vasculature as the guide wire ispositioned by the physician. Once the guide wire is in proper positionin the vasculature, the embolic filter can be deployed to captureembolic debris. The guide wire can then be used by the physician todeliver interventional devices, such as a balloon angioplasty dilatationcatheter or a stent delivery catheter, to perform the interventionalprocedure in the area of treatment. After the procedure is completed, arecovery sheath can be delivered over the guide wire using over-the-wiretechniques to collapse the expanded filter for removal from thepatient's vasculature.

When the treatment area is positioned proximate and upstream to a vesselbifurcation, it is sometimes necessary to place a single embolic filterin each of the branches of the bifurcated vessel. Utilizing a separatefilter for each branch of the artery, however, can require the use of alarger delivery catheter and may occupy more space within the treatmentsite. As the filter for each branch of the vessel must be delivered anddeployed individually, the use of multiple filters requires additionaltime to route and deploy the filters. Also, as the embolic filters arebeing removed from the branch vessels, captured embolic particles may bereleased from the filters and flow downstream through voids between thefilters and a special interventional device which has a large lumen inorder to cross over both wires.

What has been needed is an expandable filter assembly for use inbifurcated vessels which can be deployed within, and retrieved from,each branch of the vessel simultaneously. An expandable filter also isneeded which reduces the voids encountered between the individualfilters and the vessel wall during retrieval of individual filters fromthe branches of a bifurcated vessel. The present invention satisfiesthese and other needs.

SUMMARY OF THE INVENTION

The present invention provides a bifurcated embolic protection devicewhich is designed to remove emboli from bifurcated biological vessels.The present invention includes a bifurcated embolic filter having legswhich may be dispersed into individual branches of a bifurcated vesselwhile minimizing voids between the filter and the bifurcated vessel. Inthis manner, the possibility of emboli floating downstream througheither of the branch vessels is minimized.

In one aspect of the present invention, an embolic filtering device foruse in a bifurcated biological vessel includes a delivery device havinga first guide wire for directing the embolic filtering device to a firstbranch of the bifurcated vessel. The first guide wire has a proximal endand a distal end. The delivery device also has a second guide wire fordirecting the embolic filtering device to a second branch of thebifurcated vessel. This second guide wire also has a proximal end and adistal end. The second guide wire is coupled to the first guide wire andprojects distally from a distal-end region of the first guide wire. Theintersection between the first guide wire and the second guide wireforms a junction.

The embolic filtering device includes a filter support having a firstdeployment member and a second deployment member. In one aspect of thepresent invention, the first deployment member can be formed anexpandable first loop and the second deployment member formed as anexpandable second loop. Each of the first and second loops includes afirst end, a second end and an apex positioned between the first end andthe second end. The first and second ends of the first and second loopsare coupled to the first guide wire at a position proximate to thejunction between the first guide wire and the second guide wire andproximal to the junction. Each of the first and second loops includes apreset deflection proximate the first end and second end of the loop topermit the loop to diverge from a longitudinal axis of the first guidewire at the deflection of the loop.

The embolic filtering device further includes a filter element having anopening at a proximal end coupled to the filter support. The filterelement includes a first leg which extends distally toward the distalend of the first guide wire from the first loop of the filter support.The first leg tapers toward a distal end of the first leg. The filterelement includes a second leg which extends distally toward the distalend of the second guide wire from the second loop of the filter support.The second leg tapers toward a distal end of the second leg. The distalends of the first leg and the second leg each include an aperture. Thefilter element further includes a crotch at a junction between the firstleg and the second leg. With the filter element coupled to the filtersupport, the crotch of the filter element is positioned distal to thejunction between the first guide wire and the second guide wire. Thedistal-end region of the first guide wire extends through the first legof the filter element and through the aperture at the distal end of thefirst leg of the filter element while the second guide wire extendsthrough the second leg of the filter element and through the aperture atthe distal end of the second leg of the filter element.

In a detailed aspect of the invention, the distal end of the first guidewire and the distal end of the second guide wire each includes a coiltip. In another detailed aspect, the first guide wire and the secondguide wire form a plane. A center of the first loop is positionedsubstantially on the plane between the first guide wire and the secondguide wire on a side opposite from the second guide wire. A center ofthe second loop is positioned substantially on the plane between thefirst guide wire and the second guide wire, but on the same side as thesecond guide wire. In one particular embodiment of the presentinvention, the first loop and the second loop are positionedsubstantially longitudinally aligned along the first guide wire, whilein another embodiment the first loop and the second loop are positionedlongitudinally offset along the first guide wire. In a further aspect,the size of the perimeter of the first loop and the size of theperimeter of the second loop are nonequal. The opening at the proximalend of the filter element is coupled to the first loop and to the secondloop. The opening of the filter element is coupled to a portion of theperimeter of the first loop of the filter support defined by a firstposition on the perimeter of the first loop and a second position on theperimeter of the first loop. Likewise, the opening of the filter elementcan be coupled to a portion of the perimeter of the second loop of thefilter support defined by a first position on the perimeter of thesecond loop and a second position on the perimeter of the second loop.The first position on each of the first and second loops is locatedbetween the first end of the loop and the center of the loop, while thesecond position on each of the first and second loops is located betweenthe second end of the loop and the center of the loop. In anotherdetailed aspect of the first and second guide wires, the proximal end ofthe second guide wire is coupled to the first guide wire within thedistal-end region of the first guide wire. In another detailed aspect ofthe first and second guide wires, the first guide wire further includesa hollow wire having a lumen throughout its length and an aperturewithin a wall of the wire positioned within the distal-end region of thefirst guide wire. In this aspect, the second guide wire is slidablycoupled to the first guide wire and contained within the lumen of thefirst guide wire. The proximal end of the second guide wire extendsbeyond the proximal end of the first guide wire and the distal-endregion of the second guide wire projects from the aperture of the firstguide wire. In an additional detailed aspect of the invention, thelength of the first leg of the filter element and the length of thesecond leg of the filtering element are nonequal.

In another aspect of the invention, an apparatus for filtering embolicmaterial from a bifurcated biological vessel includes the embolicfiltering device described above and a handle and a restraining sheath.The handle includes extending and retracting means. The restrainingsheath includes a proximal end, a distal end and a lumen therebetween.The proximal end of the sheath is coupled to a distal end of the handle.The delivery device is contained within the lumen of the sheath and hasa clearance fit with the sheath lumen. The filter support is extendiblebeyond the distal end of the sheath and retractable into the sheath bythe means for extending and retracting the delivery device whichcorrespondingly extends and retracts the filter support within thesheath. The first loop and the second loop are contracted andsubstantially parallel to the first guide wire upon retraction of thedelivery device into the sheath, and the first loop and the second loopbeing expanded and project away from the first guide wire upon extensionbeyond the distal end of the sheath. The opening of the filter elementis opened and closed when the first loop and second loop of the filtersupport are extended from and retracted into the sheath.

It is to be understood that the present invention is not limited by theembodiments described herein. The present invention can be used inarteries and other biological vessels. Other features and advantages ofthe present invention will become more apparent from the followingdetailed description of the invention, when taken in conjunction withthe accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a particular embodiment of an apparatusfor filtering emboli in a bifurcated biological vessel embodyingfeatures of the present invention.

FIG. 2 is an elevational view, partially in cross section, of theapparatus for filtering emboli of FIG. 1 as it is being delivered to thelocation of a bifurcated biological vessel downstream from an area to betreated.

FIG. 3 is an elevational view, partially in cross section, similar tothat shown in FIG. 2, wherein the embolic filtering device is deployedwithin the bifurcated biological vessel.

FIG. 4 is an elevational view, partially in cross section, of analternative embodiment of the guide wires of the embolic filteringdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, in which like reference numerals representlike or corresponding elements in the drawings, FIG. 1 illustrates oneparticular embodiment of an apparatus 20 for filtering embolic materialfrom a bifurcated vessel incorporating features of the presentinvention. The apparatus includes an embolic filtering device 21designed to capture embolic debris which may be created and releasedinto a bifurcated biological vessel during an interventional procedure.The embolic filtering device 21 includes an expandable bifurcated filterassembly 22 having a self-expanding filter support 24 and a bifurcatedfilter element 26 attached thereto. In this particular embodiment, theexpandable filter assembly 22 is mounted onto the distal portion of abifurcated delivery device 27 including a first elongated (solid orhollow) cylindrical shaft, such as a first guide wire 28, and a secondelongated (solid or hollow) cylindrical shaft, such as a second guidewire 29. The first guide wire has a proximal end which extends outsidethe patient and is manipulated by the physician to deliver the filterassembly into the target area in the patient's vasculature. Arestraining or delivery sheath 30 extends coaxially along the deliverydevice 27 in order to maintain the expandable filter assembly 22 in itscollapsed position until it is ready to be deployed within the patient'svasculature. The expandable filter assembly may be deployed by thephysician by simply extending the filter assembly 22 beyond the distalend of the restraining sheath 30. Alternatively, the expandable filterassembly is deployed by retracting the sheath proximally to expose theexpandable filter assembly. Once the filter assembly is extended, theself-expanding filter support 24 immediately begins to expand within thebiological vessel (see FIG. 3), causing the filter element 26 to expandas well.

The delivery device 27 extends through the filter support 24 and to thecoil tips 32, 34 of the first 28 and second 29 guide wires. Thefull-length delivery device allows the physician to control the proximalend 35 of the first guide wire in order to steer the distal coil tips32, 34 into the desired branches of the bifurcated vessel whendelivering the embolic filtering device 21 through the patient'svasculature.

In FIGS. 2 and 3, the embolic filtering device 21 is shown as it isbeing delivered within an artery 36 or other biological vessel of thepatient. More particularly, FIG. 3 shows the embolic filtering device 21in its expanded position within the patient's artery 36. This portion ofthe artery 36 has a treatment site 38 in which atherosclerotic plaque 40has built up against the inside wall 42 of an artery 36 of the patient.The filter assembly 22 is to be placed at the bifurcation 37 of thevessel which is distal to, and downstream from, the treatment site 38.For example, the therapeutic interventional procedure may include theimplantation of a stent (not shown) to increase the diameter of anoccluded artery and increase the flow of blood therethrough. It shouldbe appreciated that the embodiments of the apparatus 20 described hereinare illustrated and described by way of example only and not by way oflimitation. Also, while the present invention is described in detail asapplied to a bifurcated artery of the patient, those skilled in the artwill appreciate that it can also be used in other bifurcated biologicalvessels. Additionally, the present invention can be utilized when aphysician performs any one of a number of interventional procedureswhich generally require an embolic filtering device to capture embolicdebris created during the procedure, such as balloon angioplasty, laserangioplasty or atherectomy.

The filter support 24 includes a first deployment member shown as afirst loop 44 and a second deployment member shown as a second loop 45which, upon release from the restraining sheath 30, expand the filterelement 26 into its deployed position within the artery 36 (FIG. 3).While the deployment members are shown as self-expanding loops of wirein the present embodiment, those skilled in the art will appreciate thatthe deployment members can take on many shapes and sizes. Embolicparticles 46 created during the interventional procedure and releasedinto the bloodstream are captured within the deployed filter element 26.The filter element may include perfusion openings 48, or other suitableperfusion means, for allowing blood flow through the filter element 26.The filter element will capture embolic particles which are larger thanthe perfusion openings while allowing some blood to perfuse downstreamto vital organs. Although not shown, a balloon angioplasty catheter canbe initially introduced within the patient's vasculature in aconventional SELDINGER technique through a guiding catheter (not shown).

The delivery device 27 is disposed through the area of treatment and thedilatation catheter can be advanced over the first guide wire 28 withinthe artery 36 until the balloon portion is directly in the area oftreatment 38. The balloon of the dilatation catheter can be expanded,expanding the plaque 40 against the wall position of the plaque. Afterthe dilatation catheter is removed from the patient's vasculature, astent (not shown) could be implanted at the treatment site 38 usingover-the-wire or rapid exchange techniques to help hold and maintainthis portion of the artery 36 and help prevent restenosis from occurringin the area of treatment. The stent could be delivered to the treatmentsite on a stent delivery catheter (not shown) which is advanced from theproximal end of the first guide wire to the area of treatment.

The filtering device 21 is shown mounted to the distal portion of thedelivery device 27 with the proximal portion of the bifurcated filterelement 26 disposed in a branching portion of a trunk vessel 50 of abifurcated biological vessel. First 52 and second 54 legs of the filterelement are shown disposed within a first 56 and second 58 branch,respectively, of the bifurcated vessel. Any embolic debris 46 createdduring the interventional procedure will be released into thebloodstream and should enter the filter element 26. Once the procedureis completed, the interventional device may be removed from the patient,along with the filters. The filter assembly 22 can also be collapsed andremoved from the artery 36, taking with it any embolic debris trappedwithin the filter element 26. A recovery sheath (not shown) can bedelivered over the first guide wire 28 to collapse the filter assembly22 for removal from the patient's vasculature.

Referring again to FIG. 1, the apparatus 20 for filtering embolicmaterial from a bifurcated biological vessel may include a handle 60which functions to manipulate the embolic filtering device 21. Thehandle may be of any type known in the art, such as pistol-like grip orsyringe-type handles. FIG. 1 shows a syringe-type handle which includesa plunger 62 and a cylinder 64. The handle may include means forextending and retracting the delivery device 27 which is coupled to thehandle. For instance, in the embodiment shown the delivery device may beextended and retracted by respectively pushing and drawing the plunger.

The elongate sheath 30 includes a first end 66 (proximal end), a secondend 68 (distal end) and a lumen 70 therebetween. The proximal end 66 ofthe sheath may be coupled to a distal end 72 of the handle 60, such asat the cylinder 64, via means which are well known in the art, such aswith an adhesive or by mechanical means. The lumen of the sheath issized to contain the delivery device 27 and the filter assembly 22 witha clearance fit such that the delivery device and the filter assemblycan be translated through the lumen by the extending and retractingmeans of the handle.

The materials which can be utilized for the restraining sheath 30 can bemade from polymeric material such as cross-linked HDPE. The sheath canalternatively be made from a material such as polyolefin which hassufficient strength to hold the compressed filter support and hasrelatively low frictional characteristics to minimize any frictionbetween the filtering assembly and the sheath. Friction can be furtherreduced by applying a coat of silicone lubricant, such as Microglide®,to the inside surface of the restraining sheath before the sheath isplaced over the filtering assembly.

With further reference to FIGS. 2 and 3, the delivery device 27 iscontained within the lumen 70 of the sheath 30. The delivery deviceincludes the first guide wire 28 and the second guide wire 29. The firstguide wire 28 may be used to direct the embolic filtering device 21 tothe first branch 56 of the bifurcated vessel 36. As is specificallyshown in FIG. 1, the first guide wire 28 includes a first end 35(proximal end) and a second end 74 (distal end). The distal end of thefirst guide wire may include a coil shape 32 (coil tip) whichfacilitates in guiding the first guide wire through the vasculature andpreventing injury to the vasculature. The proximal end 35 (FIG. 1) ofthe first guide wire may be coupled to the extending means of the handle60, such as a distal end of the plunger 62 portion of the handle. Adistal-end region 76 of the first guide wire may be extendible beyondthe distal end 68 of the sheath 30 and retractable into the sheath bythe means for extending and retracting the delivery device.

The second guide wire 29 may be used to direct the embolic filteringdevice 21 to the second branch 58 of the bifurcated vessel 36. Thesecond guide wire 29 includes a first end 78 (proximal end) and a secondend 80 (distal end). The distal end 80 of the second guide wire mayinclude a coil shape 34 (coil tip) which facilitates in guiding thesecond guide wire through the vasculature and preventing injury to thevasculature. The second guide wire is coupled to the first guide wire 28and projects distally from the distal-end region 76 of the first guidewire with the intersection between the first guide wire and the secondguide wire forming a junction 82. A plane is also formed between thefirst guide wire and the second guide wire. Being coupled to the firstguide wire, the second guide wire may be extendible beyond the distalend 68 of the sheath 30 and retractable into the sheath by the means forextending and retracting the delivery device 27. Upon retraction of thedelivery device into the sheath, the second guide wire is forced to besubstantially parallel to the first guide wire. The second guide wireprojects away from the distal-end region of the first guide wire uponextension of the distal-end region of the first guide wire beyond thedistal end 68 of the sheath.

With continued reference to FIGS. 2 and 3, the delivery device 27 mayalso include a filter support 24 having an expandable first loop 44 andan expandable second loop 45. The first 44 and second 45 loops may eachbe formed from a wire having a first end 84, 86 and a second end 88, 90.The dimensions of the first 44 and second 45 loops are determined inmost cases by the size of the lumen of the vessel 36 in which embolicmaterial 46 is sought to be filtered. The first and second ends of thefirst and second loops may be coupled to the first guide wire 28 throughmethods which are well known in the art, such as soldering orsandwiching the ends of the loops between the first guide wire and anannular sleeve (not shown). The first and second loops may be coupled tothe first guide wire at a position proximate, or alternatively, distalto the junction 82 between the first guide wire and the second guidewire 29, proximal to the junction and proximate each other. The firstand second loops each diverge from a longitudinal axis of the firstguide wire. The first and second loops may each include a presetdeflection proximate the first and second ends to facilitate thedivergence of the first and second loops from the first guide wire. Thefirst loop may be positioned such that a center of the first loop islocated substantially on the plane between the first guide wire and thesecond guide wire on a side opposite the second guide wire. Similarly,the second loop may be positioned such that a center of the second loopis located substantially on the plane between the first guide wire andthe second guide wire on the same side as the second guide wire.

The first 44 and second 45 loops may be extendible beyond the distal end68 of the sheath 30 and retractable into the sheath by the means forextending and retracting the delivery device 27 which correspondinglyextends and retracts the first and second loops. When the deliverydevice 27 is retracted within the sheath 30 (FIG. 2), the first loop 44and the second loop 45 are mechanically stressed within their elasticlimits to each form a long narrow loop, with the axis of each loop beingsubstantially parallel to the longitudinal axis of the first guide wire28 as shown in FIG. 2. While in this state, an apex 92 of the first loop44 and an apex 94 of the second loop 45 each include a tight bend andconsume large areas of a cross-section of the lumen 70 of the sheath.

If the apices 92, 94 of the first 44 and second 45 loops are positionedsubstantially longitudinally aligned with each other, it may causedifficulty in retracting the delivery device 27 into the sheath 30. Tofacilitate retraction of the delivery device 27 into the sheath, thefirst loop and the second loop may be positioned longitudinally offsetalong the first guide wire 28. For example, the second loop may bepositioned either proximal or distal to the first loop along the firstguide wire. By having the first and second loops positioned offsetlongitudinally, the apices of the first and second loops enter thesheath at different times and are longitudinally offset from each otherwhen the first and second loops are contracted within the lumen of thesheath. Another means to longitudinally offset the apices of the firstand second loops when the loops are contracted within example, thesecond loop may have either a larger or a smaller periphery than thefirst loop.

A suitable composition of nickel-titanium which can be used tomanufacture the first loop 44 and the second loop 45 of the filtersupport 24 of the present invention is approximately 55% nickel and 45%titanium (by weight) with trace amounts of other elements making upabout 0.5% of the composition. The austenite transformation temperatureis between about 0° C. and 20° C. in order to achieve superelasticity athuman body temperature. The austenite temperature is measured by thebend and free recovery tangent method. The upper plateau strength isabout a minimum of 60,000 psi with an ultimate tensile strength of aminimum of about 155,000 psi. The permanent set (after applying 8%strain and unloading), is less than approximately 0.5%. The breakingelongation is a minimum of 10%. It should be appreciated that othercompositions of nickel-titanium can be utilized, as can otherself-expanding alloys, to obtain the same features of a self-expandingfilter support made in accordance with the present invention.

In one example, the first 44 and second 45 loops of the filter supportof the present invention can be fabricated from a tube or solid wire ofnickel-titanium (Nitinol) whose transformation temperature is below bodytemperature. After the loop is formed, the loop is heat treated to bestable at the desired final shape. The heat treatment also controls thetransformation temperature of the filter support such that it is superelastic at body temperature. The transformation temperature is at orbelow body temperature so that the filter support is superelastic atbody temperature. The filter support is usually implanted into thetarget vessel which is smaller than the perimeter of the filter supportin the expanded position so that the loops of the filter support apply aforce to the vessel wall to maintain the filter support in its expandedposition. It should be appreciated that the filter support can be madefrom either superelastic, stress-induced martensite NiTi or shape-memoryNiTi.

The embolic filtering device 21 may also include a filter element 26.The filter element may include an opening 96 at a first end 98 (proximalend) which is coupled to the filter support 24, such as to the first 44and second 45 loops. The opening of the filter element may be coupled toa portion of the perimeter of the first loop defined by a first position100 on the perimeter of the first loop and a second position 102 on theperimeter of the first loop. The first position on the first loop may belocated between the first end 84 of the first loop and the center of thefirst loop. The second position on the first loop may be located betweenthe second end 88 of the first loop and the center of the first loop.Likewise, the opening of the filter element may also be coupled to aportion of the perimeter of the second loop defined by a first position104 on the perimeter of the second loop and a second position 106 on theperimeter of the second loop. The first position on the second loop maybe located between the first end 86 of the second loop and the center ofthe second loop. The second position on the second loop may be locatedbetween the second end 90 of the second loop and the center of thesecond loop. As discussed earlier, the opening of the filter element maybe opened and closed when the first loop and second loop of the filtersupport are extended from and retracted into the sheath 30.

The filter element 26 also includes at least a first leg 52 and a secondleg 54 which extend distally from the opening 96 of the filter element.With the filter element coupled to the filter support 24, the first legextends distally from the first loop 44 of the filter support and taperstoward a distal end 108 of the first leg. The second leg extendsdistally from the second loop 45 of the filter support and tapers towarda distal end 110 of the second leg. The distal ends 108, 110 of thefirst and second legs may each include an aperture 112, 114. The filterelement further includes a crotch 116 positioned between the first legand the second leg. With the filter element coupled to the filtersupport, the crotch is positioned distal to the junction 82 between thefirst guide wire 28 and the second guide wire 29. The distal-end region76 of the first guide wire extends through the first leg 52 of thefilter element and projects through the aperture 112 at the distal endof the first leg. The second guide wire 29 extends through the secondleg 54 of the filter element and projects through the aperture 114 atthe distal end of the second leg. To facilitate wear resistance betweenthe filter element and the first and second guide wires, the apertures112, 114 at the distal ends of the first and second legs of the filterelement may each be lined with a sleeve 118 and the first and secondguide wires may each extend through the respective sleeve. The ends ofthe sleeves can be made from a radiopaque material, such as gold orplatinum, to increase visualization under fluoroscopy. The distal endsof the first and second legs of the filter element may be positionedlongitudinally offset from each other to reduce the cross profile of thefilter having captured embolic material therein to facilitate retractionof the embolic filter into the sheath.

In one embodiment of the present invention, the perimeter of the opening96 of the filter element 26 is bonded to the first 44 and second 45loops to secure the filter element to the filter support 24 throughmethods which are well known in the art, such as with adhesives, heatbased bonding, or both. In an alternative embodiment (not shown), thefilter element may be formed with a series of tab-like projections aboutthe opening. The tab-like projections may be wrapped around the firstand second loops of the filter support and bonded thereto through themethods described.

Polymeric materials which can be utilized to create the filteringelement include, but are not limited to, polyurethane and Gortex, acommercially available material. Other possible suitable materialsinclude ePTFE. The material can be elastic or non-elastic. The wallthickness of the filtering element can be about 0.00050-0.0050 inches.The wall thickness may vary depending on the particular materialselected. The material can be made into a pair of legs or similarlysized shapes utilizing blow-mold technology or dip technology. The otherprocess can be utilized to create the perfusion openings in the filtermaterial. The perfusion openings would, of course, be properly sized tocatch the particular size of embolic debris of interest. Holes can belazed in a spinal pattern or some similar pattern which will aid in there-wrapping of the media during closure of the device. Additionally, thefilter material can have a “set” put in it much like the “set” used indilatation balloons to make the filter element re-wrap more easily whenplaced in the collapsed position.

Referring again to the delivery device 27, FIG. 1 depicts the firstguide wire 28 as a solid wire. The second guide wire 29 is also depictedas a solid wire which is coupled to the distal-end region 76 of thefirst guide wire, such as by soldering. In this embodiment, the firstand second guide wires are delivered to the first 56 and second 58branches, respectively, of the bifurcated vessel 36 by advancing thedistal end 68 of the sheath 30 to a position distal to the treatmentsite 38 and proximal to the vessel bifurcation 37. The delivery devicemay be partially extended, thereby partially extending the filter device21, and rotated from the proximal end until the first and second guidewires are aligned with the first and second branches of the bifurcatedvessel. The delivery device and first and second guide wires can then befurther extended beyond the distal end of the sheath with the distal-endregion 76 (FIG. 4) of the first guide wire 28 entering the first vesselbranch and the distal-end region 120 of the second guide wire enteringthe second vessel branch. The first 52 and second 54 legs of the filterelement 26 also enter the first and second vessel branches with thefirst and second guide wires, respectively. Further extension of thedelivery device causes expansion of the filter support 24 within thetrunk portion 50 of the vessel, thereby causing opening of the proximalend 98 of the filter element and completing deployment of the filterelement.

In an alternative embodiment, FIG. 4 depicts the first guide wire 28 asa hollow tubular member which acts as a guide wire, such as a hypotubeor polymeric tubing, having a lumen 121 throughout its length. Thesecond guide wire 29 may include a solid or hollow wire which isslidably coupled to the first guide wire and contained within the lumenof the first guide wire. The proximal end 78 of the second guide wire 29extends beyond the proximal end 35 of the first guide wire and thedistal-end region 120 of the second guide wire projects from an aperture122 within the wall of the distal-end region 76 of the first guide wire.Delivery of the first and second guide wires of this embodiment issimilar to the method described above. However, the second guide wiremay be translated proximally or distally from the proximal end tofacilitate insertion of the distal-end region of the second guide wireand the second leg 54 of the filter element 26 into the second vesselbranch 58.

The bifurcated filter of the present invention permits filtering of eachof the branches of the bifurcated vessel and the branching portion ofthe trunk vessel with a single filter without any open voids between thefilter and the vessel. As a result, the possibility of embolic materialfloating downstream through either of the branch vessels is minimized.

Further modifications and improvements may additionally be made to thedevice and method disclosed herein without departing from the scope ofthe present invention. Accordingly, it is not intended that theinvention be limited, except as by the appended claims.

1-57. (canceled)
 58. A dual guide wire system, comprising: a first guidewire having a proximal end and a distal end; and a second guide wirehaving a proximal end and a distal end, the second guide wire beingcoupled to the first guide wire and projecting distally from adistal-end region of the first guide wire.
 59. The dual guide wiresystem of claim 58, wherein the second guide wire is made from anickel-titanium alloy.
 60. The dual guide wire system of claim 58,wherein the second guide wire is made from a nickel-titanium alloy. 61.The dual guide wire system of claim 58, wherein the second guide wire ismade from a nickel-titanium alloy.
 62. A dual guide wire system,comprising: a first guide wire made from a hollow tubular member havinga lumen throughout its length and an aperture within a wall of thetubular member positioned within the distal-end region; and a secondguide wire having a proximal end and a distal end, the second guide wirebeing slidable within the lumen of the first guide wire, the distal endof the second guide wire extending through the aperture in the firstguide wire.
 63. The dual guide wire system of claim 62, wherein theaperture in the first guide wire is a slot.
 64. The dual guide wiresystem of claim 62, wherein the aperture in the first guide wire directsthe distal end of the second guide wire in a particular directionrelative to the position of the distal end portion of the first guidewire.
 65. The dual guide wire system of claim 62, wherein the secondguide wire is made from a nickel-titanium alloy.
 66. The dual guide wiresystem of claim 62, wherein the first guide wire includes a structurefor holding a filter device.
 67. The dual guide wire system of claim 66,wherein the structure is movable between a collapsed position and anexpanded position.
 68. The dual guide wire system of claim 62, whereinthe distal portion of the second guide wire is biased to move away fromthe first guide wire.